vlax-curve-getclosestpointto doesn't work as expected with splines

[dbroad]

Some may already know this but I couldn't find any documentation about the fact that the only points retrieved from the vlax-curve-getclosestpointto for splines are their control vertiices, NOT THE ACTUAL CURVE.

Try this to test.  I was surprised.

(SETQ E (CAR(ENTSEL "\nSelect a spline object: ")))
(while (setq pt (getpoint "\nPick point: "))
  (command "line" pt (vlax-curve-getclosestpointto e pt) "")
  )

 Even working outside of lisp, perpendicular snaps are unreliable.  Using AutoCAD 2023.

[ronjonp]

I don't see that behavior in AutoCAD 2025.

[dbroad]

This is what I see

[video]

After you posted your video, I tested it on AutoCAD 2018 and it worked fine so it must've been a flaw in 2023.

[ronjonp]

@dbroad 

Weird! Must be a bug in the older release. Do you have all your service packs up to date?

[dbroad]

Just installed SP2023.1.6 but it didn't help.  Weird is an understatement.  Thanks for testing.  Glad it's working in 2025.

Kind of fascinating if it wasn't so frustrating.

[daniel_cadext]

I tried this in 2021 and 2023, spine type 5 & 6, no issues. Maybe post a sample drawing?

[phanaem]

Hi

Seems like it jumps to Osnap points. I guess the regular Osnap is off, but make sure 3DOsnap (F4) is off as well.

Or just use entmakex.

[komondormrex · Accepted solution]

to be sure that was autocad bug try this

(SETQ E (CAR(ENTSEL "\nSelect a spline object: ")))
(while (setq pt (getpoint "\nPick point: "))
  (command "line" "_non" pt "_non" (vlax-curve-getclosestpointto e pt) "")
)

[dbroad]

@phanaem It jumps to the control points rather than the curve itself.

[phanaem · Accepted solution]

---

@dbroad wrote:

@phanaem It jumps to the control points rather than the curve itself.

---

Yes, because 3D Osnap is active.

Turn it off with F4, use "_none" in (Command...  line, ore use entmakex for lines.

vlax-curve-getclosestpointto works just fine with Splines.

[dbroad]

@komondormrex That worked correctly.  I'd turned off the osnaps and cleared all of the osnap choices.  Turned out that the problem was 3DOSMODE.  Thanks everyone.  No real bug but 3DOSMODE could really mess up programs that relate to splines because it's easy to overlook.